Gas turbine engines such as those used in industrial, marine, vehicle, and aerojet applications, may include multiple stages of compressors. In a typical arrangement air is first drawn over a first compressor stage that elevates the air pressure to a desired level. The air, while passing in a generally axial direction through the engine, then crosses successive compressor stages that further raise the air pressure.
It has been found that bleed valves can be used at various points on a gas turbine engine to assist in maintaining a desired level of air pressure within the engine. One point in a gas turbine engine where bleed valves are used is in the various compressor stages. Thus a bleed valve or valves may be used to control undesired effects such as engine surge. It is also desirable to activate bleed valves used in turbine engines with a pressure source drawn from a turbine engine compressor stage.
Solenoid control valves may be used to activate gas turbine bleed valves. Additionally, solenoid-activated control valves may be used in a variety of applications to regulate fluid control. Generally, solenoid activated valves are useful in that they may be controlled by electronic or computerized control systems. An electronic control system may itself provide the command to provide the electrical current that activates a solenoid valve. The electronic and computerized control is a useful feature in gas turbine engine control systems.
While certain valve designs are known that use solenoid activation, there is need for an improved design.
Weight considerations are significant criteria in control valve design. Especially in those gas turbine engines intended for use in aerojet applications, it is desired that weight be minimized. Thus it is desired that a solenoid control valve be provided that has a weight lower than control valves now available.
One function of the solenoid control valve is to pass an activating force, often a pressurized fluid such as air, through the solenoid valve and onto the bleed valve. It is desired that the activating force/pressurized fluid also provide the force necessary to open and close the solenoid valve. Thus there is a need for a solenoid control valve that can be opened and closed using a single source of activating pressure from the same pressurized fluid that is passed through the solenoid control valve.
Another important criteria in a solenoid control valve, and particularly one used to control bleed valve operation in a gas turbine engine, is response time. A quick response time is desired.
Reliability of design is another important criteria in a solenoid control valve. A design with minimum moving parts is preferred in order to lessen the need for maintenance or the chance of breakdown. What moving parts are used should be robust and simple in function. Redundancy is also a desired feature in a control valve, particularly in aerojet applications. With duplicate or redundant features, even in the event of a partial system failure, the valve will nevertheless continue to perform as desired.
An additional feature that is important in the design of a solenoid control valve is how the valve will interact with a downstream valve. Where, for example, a compressor bleed valve is connected downstream from a solenoid control valve, the design of the solenoid control valve must make allowance for the bleed valve to compress and decompress. Thus, it is a desirable feature that a flow through solenoid control valve permit pressure that is passed downstream to a bleed valve, or other type of valve, to pass back through the solenoid control valve when the downstream valve deactivates and/or decompresses.
The solenoid control valve is in the closed position during the majority of time when the engine is running. Thus, it is desired that the de-energized position of the solenoid control valve correspond to the closed position of the valve.
Hence there is a need for a solenoid control valve that addresses one or more of the above-noted objectives. That is there is a need for a solenoid control valve of minimal weight and/or with a quick response time and/or with good reliability and/or that can operate with a single pressure as the pressure supply and/or a solenoid control valve that is closed in the de-energized position. The solenoid control valve embodiment disclosed herein addresses one or more of these needs.